The iPhone can demand a password each time it wakes up, if you like.

You can’t use any other company’s SIM card in the iPhone – it’s not an “unlocked” GSM phone (at least, not officially; there are some unauthorized ways). Other recent AT&T cards work, but only after you first activate them. Insert the other card – it fits only one way, with the AT&T logo facing up – then connect the iPhone to your computer and let the iTunes software walk you through the process.

Geeks may enjoy knowing that the screen is 320 by 480 pixels.

On the iPhone 3G, you can use any standard headphones with the iPhone – a welcome bit of news for audiophiles who don’t think the included earbuds do their music justice. But on the original iPhone, the molding around the iPhone’s audio jack prevents most miniplugs from going all the way. You must be able to get your headphones to fit by trimming the plastic collar with a razor blade – or you can spend $10 for a headphone adapter (from Belkin.com, among others) to get around this problem.

Camouflaged behind the black glass above the earpiece, where you can’t see them except with a bright flashlight, are two sensors. First, there’s an ambient-light sensor that brightens the display when you’re in sunlight and dims it in darker places. You can also adjust the brightness manually. Second, there’s a proximity sensor. When something (like your head) is close to the sensor when you’re using the phone functions, it shuts off the screen illumination and touch sensitivity. Try it out with your hand. (It works only in the iPhone application.) You save power and avoid tapping buttons with your cheekbone.

With practice, you can learn to tell if the ringer is on while the iPhone is still in your pocket. That’s because when the ringer is on, the switch falls in a straight line with the volume keys. By swiping your thumb across these controls from front to back, you can feel whether teh silencer switch is lined up or tilted away.

There’s only one payoff for knowing what’s down here: The speakerphone isn’t very loud, because it’s aimed straight out of the iPhone’s edge, away from you. If you cup your hand around the bottom edge, you can redirect the sound toward your face, for an immediate boost in volume and quality.

You may have noticed one standard cellphone feature that’s not here: the battery compartment door. The battery isn’t user-replaceable. It’s rechargeable, of course – it charges whenever it’s in the white dock or connected via the USB cable – but after 300 or 400 charges, it will start to hold less juice. Eventually, you’ll have to pay Apple to install a new battery. (Apple says that the added bulk of a protective plastic battery compartment, a removable door and latch, and battery retaining springs would have meant a much smaller battery – or a much thicker iPhone).

Because the period is such a frequently used symbol, there’s a little shortcut that doesn’t require switching to the punctuation keyboard: at the end of a sentence, just tap the Space bar twice. You get a period, a space, and a capitalized letter at the beginning of the next word. (This, too can be turned off, although it’s hard to imagine why you’d want to.)

Although you don’t see it, the sizes of the keys on the iPhone keyboard are actually changing all the time. That is, the software enlarges the “landing area” of certain keys, based on probability. For example, suppose you type tim. Now, the iPhone knows that no word in the language begins timw or timr – and so, invisbly, it enlarges the “landing area” of the E key, which greatly diminshes your chances of making a typo on that last letter. Cool.

In the Safari address bar, you can skip the part above waiting for the Loupe to appear. Once you’ve clicked into the address, just start dragging to make it appear at once.

In bright light, the screen brightens (but uses more battery power). In dim light, it darkens. This happens because of an ambient-light sensor that’s hiding behind the glass above the earpiece. Apple says that it tried having the light sensor active all the time, but it was weird to have the screen constantly dimming and brightening as you used it. So the sensor now samples the ambient light and adjusts the brightnes only once – when you unlock the phone after waking it.

Incoming calls pause video playbacks. In this case, though, hanging up does not make video playback resume. Instead, the screen displays a list of videos. Apple says it’s a bug.

Remember that the speaker is on the bottom edge. If you’re having trouble hearing it, and the volume is all the way up, consider pointing the speaker toward you, or even cupping one hand around the bottom to direct the sound.

Ordinarily, the Contact list sorts names alphabetically, either by first name or last name. There’s no way to sort it by company name… or is there? Yes, there is. When you’re creating a contact, tap the First Last box – but enter only a company name (in the Company box). Then save the entry. If you bother to go all the way back to Contacts, you’ll see that the entry is now alphabetized by the company name. You can now reopen it for editing and add the person’s name and other information. The entry will remain in the list, identified (and sorted) by company name.

If you know that somebody has AT&T like you, add “(AT&T)” after the last name. That way, when he calls you, you’ll know that the call is free (like all AT&T-to-AT&T calls).

On the iPhone, buttons that mean “Save,” “OK,” or “Done” always appear in a blue box, where they’re easy to spot.

iPhones

iPhone is one of the most incredible handheld devices. Of course, the iPhone is one heck of a wireless telephone, but it’s actually four awesome handheld devices in one. In addition to being a killer cell phone, it’s a gorgeous widescreen video iPod, a decent 2-megapixel digital camera (original iPhone and iPhone 3G) or 3-megapixel camera/camcorder (iPhone 3GS), as well as the smallest, most powerful Internet communication device yet.

The iPhone has many best-of-class features, but perhaps its most unusual feature is the lack of a physical keyboard or stylus. Instead, it has a 3.5-inch super-high-resolution touchscreen (160 pixels per inch if you care about such things) that you operate using a pointing device you’re already intimately familiar with: your finger. And what a display it is. We venture that you’ve never seen a more beautiful screen on a handhelf device in your life.

iPhone has another feature that can knock your socks off – built-in sensors. An accelerometer detects when you rotate the device from portrait to landscape mode and adjusts what’s on the display accordingly. A proximity sensor detects when the iPhone gets near your face, so it can turn off the display to save power and prevent accidental touches by your check. And a light sensor adjusts the display’s brightness in response to the current ambient lighing situation.

The iPhone as a phone and digital camera/camcorder
On the phone side, the iPhone synchronizes with the contacts and calendars on your Mac or PC. It includes a full featured QWERTY soft, or virtual, keyboard, which makes typing text easier than ever before – for some folks.

Granted, the virtual keyboard takes a bit of time to get used to. But we think that many of you eventually will be whizzing along at a much faster pace than you thought possible on a mobile keyboard of this type.

The 2-megapixel (iPhone and iPhone 3G) or 3-megapixel (iPhone 3GS) digital camera is accompanied by a decent photo management applications, so taking and managing digital photos (and videos on iPhone 3GS) is a pleasure rather than the nightmare it can be on other phones. Plus, you can automatically synchronize iPhone photos and videos with the digital photo library on your Mac or PC. Okay, we still wish the iPhone camera took better photos and shot better video but it is still much better than most other phone cameras.

Finally, one of our favorite phone accountrements is visual voicemail. This feature lets you see a list of voicemail messages and choose which ones to listen to or delete without being forced to deal with every message in your voice mailbox in sequential order. Now, that’s handy!

The iPhone as an iPod We agree with Steve Jobs on this one: The iPhone is a better iPod than almost any that Apple has ever made. (Okay, we can quibble about the iPod Touch or wanting more storage.) You can enjoy all your existing iPod content – music, audiobooks, audio and video podcasts, music videos, television shows, and movies – on the iPhone’s gorgeous high-resolution color display, which is bigger, brighter, and richer than any iPod display that came before it.

Bottom line: If you can get the content – be it video, audio, or whatever – into iTunes on your Mac or PC, you can synchronize it and watch or listen to it on you iPhone.

The iPhone as an Internet communications device
But wait – there’s more! Not only is the iPhone a great phone and a stellar iPod, but it’s also a full-featured Internet communications device with – we’re about to drop a bit of industry jargon on you – a rich HTML, e-mail client that’s compatible with most POP and IMAP mail services, with support for Microsoft Exchange ActiveSync. Also on board is a world-class Web browser (Safari) that, unlike on other phones, makes Web surfing fun and easy.

Another cool Internet feature is Maps, a killer mapping application based on Google Maps. By using GPS (3G or 3GS hardware) or triangulation (on the original iPhone), it can determine your location, let you view maps and satellite imagery, and obtain driving directions and traffic information regardless of where in the United States you happen to be. You can also find businesses such as gas stations, pizza restaurants, hospitals, and Apple stores with just a few taps. And the Compass application (3GS only) not only displays your current GPS co-ordinates but also orients Maps to show the direction you’re facing. Let’s see your Nokia do that!

You might also enjoy using Stocks, a built-in application that delivers near real-time stock quotes and charts any time and any place, or Weather, another built-in app that obtains and displays the weather forecast for as many cities as you like.

The Internet experience on an iPhone is far superior to the Internet experience on any other handheld device.

Technical specifications
Here’s a list of everthing you need before you can actually use your iPhone:

• An original iPhone, iPhone 3G, or the new iPhone 3GS
• A wireless contract with AT&T (formerly Cingular) in the US
• An iTunes Store account
• Internet access (required) – broadband wireless Internet access recommended

Plus you need one of the following

• A Mac with a USB 2.0 port; Mac OS X version 10.4.11 or later; and iTunes 8.2 or later
• A PC with a USB 2.0 port; Windows Vista or Windows XP Home or Professional with Service Pack 2 or later; and iTunes 8.2 or later